This project involves the development of a cardiopulmonary bypass system utilizing a membrane oxygenator which does not require systemic heparinization. Heparin is bound to the surfaces of the equipment by a chemical process. Initial results in seven animals perfused up to five days successfully have been encouraging. Clots have been found in areas of th membrane where the silicone films are bound to the casing of the oxygenator. All animals have survived, and no clots have been found in any on microscopic exam. Future efforts will efforts will be directed at redesigning the oxygenator to prevent stasis of blood.